Lassie finds a beautiful wild black stallion who has injured his leg, so Corey adopts him. The horse, however, misses his herd so Lassie sets him free. After the herd's new leader drives him away, he returns to Corey and his new life.
Lassie is injured when she defends a mountain lion's cub from a wild dog. The cub's mother leads Lassie to water, takes her back to their den to recover, and brings food. Lassie returns the cat's kindness when a hunter tries to shoot her.
Lassie and Corey help Jack deliver special salt blocks to a herd of Bighorn sheep. The males battle for supremacy which leaves an old ram injured. Since there is a wild dog pack in the area, Lassie is concerned about the old ram.
Out on one of her nature walks, Lassie helps an owl family survive after the mother owl is injured by an opossum, Lassie hides and feeds the injured owl and provides a surrogate mother for the owl's eggs until the mother owl can return.
White Horse Falls, a logging town, is failing due to poor lumber management. Corey helps the town by demonstrating new timber technology while Lassie watches over Henry IV, a kitten with a penchant for getting into all types of trouble.
While Corey works with locals on a soil management project, Lassie befriends a German Shepherd and a coyote. When the coyote is shot illegally by a hunter, Lassie brings Corey to doctor the coyote and deal with the hunter.
Barney is a watch dog at a turkey game preserve. He lost a fight to a bob cat and has lost his spirit. When Lassie gets tangled in barbed wire and is prey to the bobcat, Barney comes to her rescue.and gets his fighting spirit back.
A house painter hired to paint the ranger station goes fishing and loses his good luck charm. After two days of bad luck he asks that Lassie help him. A squirrel has the charm and Lassie trades with the squirrel to retrieve the charm.
Lassie prevents a pigeon from attack by a hawk earning the gratitude of Eddie, the pigeon's owner. Spending time with the young man, Lassie goesable for help when Eddie falls down an isolated mine shaft.
Goliath is a huge steer and tourist attraction at a roadside cafe. When the abusive owner beats Goliath. he escapes and injures and man. Lassie helps Goliath hide and leads him away from the men trying to shoot him until Corey can arrive.
Lassie and Corey visit old Ben where Lassie meets the otters. When one otter is trapped, the other comes for help. Ben destroys the traps but meets the angry neighbor who want the otters gone. Corey explains how the otters help the lake.
While Corey examines an area to assess damage after an earthquake, Lassie becomes involved with first a duck and then a prairie dog town who are rebuilding after the quake. Then an aftershock brings even more trouble.
Corey and Bart enlist a sail plane pilot to learn about wind sheers, while Lassie helps a pregnant cougar who has been mistakenly shot by a farmer for raiding his chickens. The real culprit is a feral dog.
A wild animal is by night stealing poultry and frightening the horse Starfire. The foreman thinks it is a cougar who has done this and wants to shoot it, but Lassie understands that the cougar is innocent. When Lassie finds out that the cougar has cubs but is too wounded to feed them, Lassie has to find meat for them and protect all of them from being shot.
Corey and Jack fix the plane before the storm breaks, but every pound is precious. When Jack insists that the aircraft will not be able to take off with Lassie's added weight, Corey rigs a device so she can be picked up after the plane is in the air.
In his capacity as advisor for a new balloon logging project, Corey inspects a tugboat operation. Corey and Lassie journey on two different boats. When the pilot of Lassie's boat has a stroke, Lassie must find Corey to get help for him..
At the Wind River tree nursery deer are eating the seedling trees. Rather than see the deer shot, Lassie moves the family of deer across a bridge into a wildlife preserve. When the fawn strays into the river, Lassie helps it to safety.
Delivering trees on Christmas Eve, Lassie and Corey find and free a dove tangled up in brush. The dove repays the favor by leading Lassie to a little girl's lost puppy so that Lassie can return it to the worried child.
Out delivering treats to her forest friends, Lassie finds a lost black lamb. She reunites that lamb with its mother only to find a lost white lamb. After finding that lamb's mother, Lassie finds a lost black and white lamb. She howls her frustration before setting out to find that lamb's mother.